Lung 4D-CT plays an important role in lung cancer radiotherapy.However

due to the great inter-slice thickness

the fuzzy images will be induced because of interpolation operation during the multi-plane display.In this paper

we take the low-resolution images of different phases in the corresponding position as different frame images

and propose a registration based super-resolution reconstruction method to improve the resolution of lung 4D-CT images.First

we employ the Active Demons registration to estimate the motion field between different frames.Then

the projection onto convex set (POCS) approach is employed to reconstruction high-resolution lung images.The experimental results show that our method can get more clear lung images and significantly enhance image structure

compared with the cubic spline interpolation and back projection method.